In-vehicle image display system and image processing method

ABSTRACT

Disclosed is an in-vehicle image display device equipped in a vehicle to support driving of a driver. The in-vehicle image display system comprises: a side camera installed to a lateral portion of an exterior of the vehicle to face outwardly and configured to take an image of an area lateral to the vehicle by using a wide-angle lens; a processing unit configured to correct a wide-angle image taken by the side camera to generate a planar image, and process the planar image to generate a processed image; and a display unit configured to display the processed image transmitted from the processing unit on a screen, wherein the processing unit is operable to execute a secondary processing of the planar image so as not to include an image region located outward from the reachable position in a vehicle-width direction, in order to generate the processed image.

TECHNICAL FIELD

The present invention relates to an in-vehicle image display system andan image processing method, and more particularly to an in-vehicle imagedisplay system which is equipped in a vehicle to support driving of adriver, and an image processing method.

BACKGROUND ART

Heretofore, there has been known an in-vehicle image display systemconfigured to take images around a vehicle, and display the taken imageson a monitor installed in the vehicle, thereby supporting driving of adriver. For example, when the driver is trying to park the vehicle, thissystem is operable to take an image of an area around the vehicle whichis a blind spot of the driver, and display the taken image on themonitor, thereby supporting the driver to check safety of thesurroundings of the vehicle. For this purpose, the system employs acamera which is equipped with a wide-angle lens (a fisheye lens or thelike), and capable of taking an image in a wider range.

An image taken by the wide-angle lens-equipped camera is formed suchthat it is gradually compressed (shrunk) in a direction getting awayfrom an optical axis of the lens, resulting in the occurrence of“distortion”. This “distortion” leads to difficulty in visual checkingof a peripheral region of the image. As means to solve this problem,there has been known an in-vehicle image display system configured tosubject an image taken by a wide-angle lens-equipped camera tocoordinate conversion, to enable the taken image to be displayed on amonitor in the form of a planar image free of “distortion” (e.g., thefollowing Patent Document 1 or 2).

CITATION LIST Patent Document

Patent Document 1: JP 2016-143381A

Patent Document 2: JP 2016-167792A

SUMMARY OF INVENTION Technical Problem

However, in the planar image obtained by subjecting the image taken bythe wide-angle lens-equipped camera to coordinate conversion, aperipheral region thereof is composed of a less number of pixels ascompared with a central region thereof, so that “blur” occurs in aregion of the planar image away from the optical axis. Therefore, thereis still the problem that a driver has difficulty in visually checkingthe peripheral region. Further, generally, an installation position ofthe camera with respect to a vehicle is determined in consideration ofvehicle exterior design and surrounding components, withoutconsideration for “blur” in an image displayed on the monitor. That is,when an area around a vehicle to be watched for safety purposes by adriver is displayed on the monitor, there is a possibility that “blur”occurs in a part of the image, thereby leading to a problem that thedriver has difficulty in visually checking the part. This also causes aproblem that the driver is preoccupied with checking the “blurred” part,and thus driver's attentiveness to driving is likely to be lowered.

It is therefore an object of the present invention to an in-vehicleimage display system and an image processing method which are capableof, when displaying, to a driver, an image taken by a wide-anglelens-equipped camera, preventing lowering of attentiveness of thedriver, thereby supporting safety drive of the driver. [Solution toTechnical Problem]

In order to solve the above problem, the present invention provides anin-vehicle image display system equipped in a vehicle to support drivingof a driver. The in-vehicle image display system comprises: a sidecamera installed to a lateral portion of an exterior of the vehicle toface outwardly and configured to take an image of an area lateral to thevehicle by using a wide-angle lens; a processing unit configured tocorrect a wide-angle image taken by the side camera to generate a planarimage, and process the planar image to generate a processed image; and adisplay unit configured to display the processed image transmitted fromthe processing unit on a screen, wherein the processing unit is operableto set a position of the vehicle at a predetermined setup vehicle speed,as a reference position, wherein the processing unit is operable to seta position which is reached by a part of a contour of the vehiclelocated at a farthermost position with respect to a center of thevehicle in the reference position as a reachable position, in a positionof vehicle where the vehicle has stopped by being decelerated from thereference position under a maximum steering angle and a predeterminedbraking force, and wherein the processing unit is operable to execute asecondary processing of the planar image so as not to include an imageregion located outward from the reachable position in a vehicle-widthdirection, in order to generate the processed image.

In the in-vehicle image display system of the present invention havingthe above feature, the secondary processing is executed so as not toinclude an image region of a peripheral road surface section which islocated outward, in the vehicle-width direction, of the reachableposition and in which “blur” is highly likely to occur. Therefore, thedriver can visually check the traveling road surface section to bewatched for safety purposes, without being preoccupied with theperipheral road surface section, so that it is possible to preventdistraction of the driver's attentiveness, thereby supporting safetydrive of the driver.

Preferably, in the in-vehicle image display system of the presentinvention, the reachable position is defined based on: a free runningdistance which is a traveling distance of the vehicle in thevehicle-width direction as measured based on the setup vehicle speed andthe maximum steering angle during a time period from a time when thedriver recognizes an object through until the driver starts a brakingaction: and a braking distance which is a traveling distance of thevehicle in the vehicle-width direction as measured based on the setupvehicle speed and the maximum steering angle during a time period from atime when the driver starts the braking action through until the vehicleis stopped. According to this feature, the traveling road surfacesection in the vehicle-width direction can be set accurately, so that itis possible to adequately perform the secondary processing so as not toinclude an image region of the peripheral road surface section.

Preferably, in the in-vehicle image display system of the presentinvention, an optical axis of the wide-angle lens is set to extendtoward a give position of a traveling road surface section, such that acontrast ratio in an image region of the traveling road surface sectiontaken until the part of the contour of the vehicle reaches the reachableposition becomes 30% or more. According to this feature, no “blur”occurs in the traveling road surface section displayed on the screen, sothat the driver can visually check the traveling road surface section ina “blur”-free state.

In order to solve the above problem, the present invention also providesan image processing method for an in-vehicle image display system forsupporting driving of a driver. The image processing method comprisesthe steps of: receiving a wide-angle image taken by a side cameraconfigured to take an image of an area lateral to a vehicle, through awide-angle lens of the side camera; correcting the wide-angle image togenerate a planar image, and processing the planar image to generate aprocessed image; setting a position of the vehicle at a predeterminedsetup vehicle speed, as a reference position; setting a position whichis reached by a part of a contour of the vehicle located at afarthermost position with respect to a center of the vehicle in thereference position as a reachable position, in a position of vehiclewhere the vehicle has stopped by being decelerated from the referenceposition under a maximum steering angle and a predetermined brakingforce; and executing a secondary processing of the planar image so asnot to include an image region located outward from the reachableposition in a vehicle-width direction, in order to generate theprocessed image.

In the present invention having the above feature, there is provided animage processing method in which the secondary processing is executed soas not to include an image region of a peripheral road surface sectionwhich is located outward, in the vehicle-width direction, of thereachable position and in which “blur” is highly likely to occur.Therefore, the driver can visually check the traveling road surfacesection to be watched for safety purposes, without being preoccupiedwith the peripheral road surface section, so that it is possible toprevent distraction of the driver's attentiveness, thereby supportingsafety drive of the driver.

Effect of Invention

The in-vehicle image display system and the image processing method ofthe present invention are capable of, when displaying, to a driver, animage taken by a wide-angle lens-equipped camera, preventing lowering ofattentiveness of the driver, thereby supporting safety drive of thedriver.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a side view showing the entirety of a vehicle equipped withan in-vehicle image display system according to one embodiment of thepresent invention.

FIG. 1B is a top plan view of the vehicle in FIG. 1A.

FIG. 2 is a diagram showing a basic configuration of the in-vehicleimage display system according to this embodiment.

FIG. 3A is a diagram showing a state of vehicle handling using thein-vehicle image display system according to this embodiment.

FIG. 3B is a diagram showing a state of display on a liquid crystaldisplay during the vehicle handling in FIG. 3A.

FIG. 4A is a diagram showing an example of a planar image obtained bycorrecting a wide-angle image taken by a wide-angle lens-equippedcamera.

FIG. 4B is a diagram showing an example of a processed image obtained bysubjecting the planar image in FIG. 4A to secondary processing.

FIG. 5A is an explanatory diagram of a relationship between “blur” and acontract ratio, wherein the contract ratio is 100%.

FIG. 5B is an explanatory diagram of a relationship between “blur” andthe contract ratio, wherein the contract ratio is 30%.

FIG. 5C is an explanatory diagram of a relationship between “blur” andthe contract ratio, wherein the contract ratio is 10%.

FIG. 6 is a rear view showing the vehicle equipped with the in-vehicleimage display system according to this embodiment, in association with atraveling road zone.

FIG. 7 is a top plan view of the vehicle in FIG. 6.

FIG. 8 is a flowchart showing an image processing method used in thein-vehicle image display system according to this embodiment.

FIG. 9 is a top plan view a vehicle equipped with an in-vehicle imagedisplay system according to one embodiment of the present invention, inassociation with a traveling road zone.

DESCRIPTION OF EMBODIMENTS

With reference to the accompanying drawings, an embodiment of thepresent invention will now be described.

First of all, with reference to FIGS. 1 and 2, a basic configuration ofan in-vehicle image display system according to one embodiment of thepresent invention will be described. FIG. 1A is a side view showing theentirety of a vehicle equipped with the in-vehicle image display system,and FIG. 1B is a top plan view of the vehicle in FIG. 1A. FIG. 2 is adiagram showing a basic configuration of the in-vehicle image displaysystem.

As used in this specification, a direction along which the vehicle movesforwardly and a direction along which the vehicle moves backwardly arereferred to respectively as a front (forward) side and a rear (rearward)side. Further, a vehicle-width direction of the vehicle, a verticaldirection, a direction getting away from the vehicle in vehicle-widthdirection, and a direction getting close to the vehicle are referred torespectively as a right/left (rightward/leftward) side, an upper/lower(upward/downward) side, an outer (outward) side, and an inner (inward)side.

As shown in FIGS. 1 and 2, the in-vehicle image display system 1 isequipped in a vehicle 2, and comprises a front camera 3, a rear camera5, a left side camera 7, a right side camera 9, a display unit 11, aswitch unit 13, and a processing unit 15. The in-vehicle image displaysystem 1 is configured to acquire sensor data from various sensors. Thevarious sensors include a gear position sensor 17, a vehicle speedsensor 19, and a steering angle sensor 21.

Referring to FIG. 1, the front camera 3 is installed to a front portion4 of an exterior of the vehicle 2, at a vehicle-width directional centerof a front edge of the vehicle 2. More specifically, the front camera 3is installed at a position above an ornament disposed between light andleft headlights in the front portion 4. The front camera 3 is equippedwith a wide-angle lens, and installed to face forwardly and obliquelydownwardly. The wide-angle lens is composed of, e.g., a fisheye lens oran ultrawide-angle lens, and is capable of taking a wide-angle imagehaving an angle-of-view (about 180 degrees) greater than anangle-of-view or field-of-vision of a driver. Thus, the front camera 3can take an image of a forward part of an area around the vehicle 2 in awide range through the wide-angle lens. The front camera 3 iscommunicably connected to the processing unit 15, and operable totransmit data about the taken wide-angle image to the processing unit15.

The rear camera 5 is installed to a rear portion 6 of the exterior ofthe vehicle 2, at a vehicle-width directional center of a rear end ofthe vehicle 2. More specifically, the rear camera 5 is installed at aposition above a license plate disposed between light and leftbacklights in the rear portion 6. In other words, the rear camera 5 isinstalled at a height position approximately equal to that of a loweredge of a rear windshield glass 8, i.e., in the vicinity of an uppermostedge of the rear end of the rear portion 6 as a blind spot area when thedriver looks at the rear windshield glass 8 (in the vicinity of aboundary between the blind spot area and a non-blind spot area). Thus,the rear camera 5 can take an image as if the driver viewed the blindspot area through the rear windshield glass 8. The rear camera 5 isequipped with a wide-angle lens having the same specifications as thoseof the wide-angle lens of the front camera 3, and installed to facerearwardly and obliquely downwardly. Thus, the rear camera 5 can take animage of a rearward part of the area around the vehicle 2 in a widerange through the wide-angle lens. The rear camera 5 is communicablyconnected to the processing unit 15, and operable to transmit data aboutthe taken wide-angle image to the processing unit 15.

The left side camera 7 and the right side camera 9 are installed,respectively, to opposite lateral portions 12 of the exterior of thevehicle 2, at positions below left and right door mirrors 10. Each ofthe left and right side cameras 7, 9 is equipped with a wide-angle lenshaving the same specifications as those of the wide-angle lens of thefront camera 3, and installed to face outwardly and obliquelydownwardly. Thus, each of the left and right side cameras 7, 9 can takean image of a lateral part of the area around the vehicle 2 in a widerange through the wide-angle lens. Each of the left and right sidecameras 7, 9 is communicably connected to the processing unit 15, andoperable to transmit data about the taken wide-angle image to theprocessing unit 15.

The display unit 11 is equipped with as liquid crystal screen fordisplaying an image thereon, and installed onto a dashboard at a frontend of a passenger compartment of the vehicle 2. Here, a liquid crystalscreen for a car navigation system may be additionally used as thisdisplay unit 11. The liquid crystal screen of the display unit 11 isinstalled to face a driver seat to allow the driver to visually checkthe screen during driving. The display unit 11 is communicably connectedto the processing unit 15, and operable to receive image data throughthe processing unit 15.

The gear position sensor 17 is electrically connected to a speed changemechanism having a plurality of gear sets. The speed change mechanismcomprises a reverse gear set for moving the vehicle 2 backwardly, and aplurality of drive gear sets for moving the vehicle 2 forwardly. Whenthe driver manipulates a shift lever to select one of the gear sets, thevehicle 2 is driven to travel in the selected vehicle travelingdirection and speed. The gear position sensor 17 is communicablyconnected to the processing unit 15, and operable to detect a positionof the shift lever and transmit gear position data to the processingunit 15.

The vehicle speed sensor 19 is operable to detect an absolute vehiclespeed of the vehicle 2. The vehicle speed sensor 19 is communicablyconnected to the processing unit 15, and operable to transmit theabsolute vehicle speed of the vehicle 2 to the processing unit 15.

The steering angle sensor 21 is operable to detect a steering angle. Thesteering angle sensor 21 is communicably connected to the processingunit 15, and operable to transmit steering angle data to the processingunit 15.

The switch unit 13 is installed in the vicinity of the display unit 11or the driver seat in the passenger compartment, and comprises a poweron-off switch 18 for selectively activating and deactivating the displayunit 11 and the cameras, and an image switching switch 20 for switchinga type of image on the display unit 11. When the shift lever is set at aposition for one of the drive gear sets, the driver can manipulate theimage switching switch 20 to select one of a forward image taken by thefront camera 3, a forward wide-range image of a wider area taken by thefront camera 3, and lateral images taken by the left and right sidecameras 7, 9 to display the selected image on the liquid crystal screen.On the other hand, when the shift lever is set at a position for thereverse gear set, the driver can manipulate the image switching switch20 to select one of a rearward image taken by the rear camera 5, and arearward wide-range image of a wider area taken by the rear camera 5, todisplay the selected image on the liquid crystal screen. Each of theswitches is communicably connected to the processing unit 15, andoperable to transmit a signal therefrom to the processing unit 15.

The processing unit 15 is a CMU (Connectivity Master Unit) and or an ECU(Electronic Control Unit) for generally managing signals and a varietyof data. The processing unit 15 is configured to receive data about thewide-angle images taken by the cameras. The professing unit 15 isoperable to subject each of the wide-angle images to coordinateconversion so as to correct the wide-angle image, thereby generating aplaner image in real time. Simultaneously, the professing unit 15 isoperable to subject each of the planer images each corresponding to arespective one of the wide-angle images taken by the left and right sidecameras 7, 9 to secondary processing, thereby generating a processedimage. Subsequently, the processing unit 15 is operable to transmit dataabout the processed images. Thus, each of the wide-angle images taken bythe left and right side cameras 7, 9 is displayed on the display unit 11as the processed image. The processing unit 15 is further operable,based on data and signals from the sensors and the switch unit 13, tocontrol a type and content of the processed image to be displayed on theliquid crystal screen of the display unit 11. In this embodiment, theprocessing unit 15 is configured to execute masking processing as oneexample of the secondary processing.

Next, with reference to FIGS. 3 and 4, a basic concept of the in-vehicleimage display system according to this embodiment will be described.FIG. 3A is a diagram showing a state of vehicle handling using thein-vehicle image display system, and FIG. 3B is a diagram showing astate of display on the liquid crystal display during the vehiclehandling in FIG. 3A. FIG. 4A is a diagram showing an example of a planarimage obtained by correcting a wide-angle image taken by the wide-anglelens-equipped camera, and FIG. 4B is a diagram showing an example of aprocessed image obtained by subjecting the planar image in FIG. 4A tothe secondary processing.

For example, the in-vehicle image display system 1 is used in asituation where the driver is trying to pull the vehicle 2 over along acurb 16 (see FIG. 3A). Upon turn-on of the power on-off switch 18 by thedriver, the in-vehicle image display system 1 is activated. Then, whenthe driver moves the shift lever to the position for one of the drivegear sets, the processing unit 15 operates to display images ofsurrounding areas lateral to the vehicle 2 taken by the side cameras 7,9, on the display unit 11. On the liquid crystal display of the displayunit 11, a direction-specific image display 24 for displaying variousimages, an icon 26 indicative of a usage state, the power on-off switch18, and the image switching switch 20 are displayed (see FIG. 3B).

In the direction-specific image display 24, the image(s) taken by thefront camera 3, the rear camera 5, or the left and right side cameras 7,9 is(are) displayed. For example, in the direction-specific imagedisplay 24 in FIG. 3B, left and right lateral images taken by the leftand right side cameras 7, 9 are displayed side-by-side. Each of thelateral images includes a parallel-to-vehicle line 28 and a vehiclefront edge line 30. The parallel-to-vehicle line 28 is a line indicativeof a measure of a vehicle width including the door mirrors 10. Thevehicle front edge line 30 is a line indicative of a measure of thefront edge of the vehicle 2. An image to be displayed in thedirection-specific image display 24 can be switched between the forwardimage and the forward wide-range image by the image switching switch 20.On the other hand, when the driver moves the shift lever to the positionfor the reverse gear sets, the rearward image or the rearward wide-rangeimage can be displayed according to the image switching switch 20.

The icon 26 denotes the position of the camera taking the imagecurrently displayed on the direction-specific image display 24.

As above, the vehicle-surrounding image of a blind spot area of thedriver taken by each of the cameras is displayed on the liquid crystalscreen of the display unit 11. Thus, the driver can drive the vehicle 2while checking safety of the surroundings of the vehicle by the liquidcrystal screen of the display unit 11.

Preferably, the processing unit is operable, when determining that theabsolute vehicle speed detected by the vehicle speed sensor 19 exceeds15 km/h, to stop the screen display of the display unit 11. As a result,any image in the direction-specific image display 24 is turned off

The lens used in each of the cameras of the in-vehicle image displaysystem 1 is composed of a wide-angle lens such as a fisheye lens and anultrawide-angle lens, wherein any taken wide-angle image is displayed asa circular image. A peripheral region of the wide-angle image is morelargely compressed as compared with a central region thereof, so that“distortion” gradually becomes larger in a direction getting away fromthe optical axis of the lens. This causes difficulty in visual checkingin the peripheral region where the “distortion” occurs.

In order to solve the “distortion” of the wide-angle image, theprocessing unit 15 operates to correct the wide-angle image by means ofcoordinate conversion to generate a planer image, as shown in FIG. 4A. Aplanar image 37 shown in FIG. 4A is a part of the planer image obtainedby correcting the wide-angle image. As a result of the correction bymeans of coordinate conversion, a peripheral region 40 of the planarimage 37 is composed of a less number of pixels as compared with acentral region 38 thereof, i.e., is insufficient in terms of the numberof pixels. Therefore, there is still the problem that the driver hasdifficulty in visually checking the peripheral region. Specifically, inthe planar image 37, “blur” gradually becomes larger in a directiongoing away from the optical axis (not illustrated). That is, theperipheral region 40 has a contrast ratio of less than 30%, and exhibits“blur”, so that it is not suitable to enable the driver to visuallycheck an imaged object. On the other hand, the central region 38 of theplanar image 37 has a contrast ratio of 30% or more, and exhibits almostno “blur”, so that it is suitable to enable the driver to visually checkan imaged object.

As above, in the planer image 37, the central region 38 is suitable toenable the driver to visually check an imaged object, and the peripheralregion 40 is not suitable to enable the driver to visually check animaged object. When a traveling road surface section to be watched bythe driver during driving is displayed in the central region 38, thedriver can immediately visually check the traveling road surfacesection. However, if a peripheral roar surface zone other than thetraveling road surface section is additionally displayed in theperipheral region 40, due to the “blur” occurring in the peripheralregion 40, the driver is preoccupied with checking the peripheral roarsurface zone, and thus driver's attentiveness to driving is likely to belowered.

FIG. 4B shows a processed image 42 obtained when the processing unit 15operates to subject the planer image 37 to the secondary processing. Inthe processed image 42, a part of an image region of the peripheral roarsurface zone comprised in the peripheral region 40 is hidden as aprocessed region 44, and an image region of the traveling road surfacesection comprised in the central region 38 is displayed directly. Inthis case, a part of the processed image region of the peripheral roarsurface zone is an image region located outward of a position away fromone of the lateral portions 12 of the vehicle in the vehicle-widthdirection by a given distance. Therefore, the driver can visually checkthe traveling road surface section without being preoccupied withchecking of the peripheral road surface section in which “bure” occurs.

Next, with reference to FIG. 5, the definition of “blur” in thisembodiment will be described. FIG. 5 is the explanatory diagram of arelationship between “blur” and the contract ratio.

As one example, “blur” is defined by the contrast ratio. The contrastratio means a value obtained by dividing a minimum luminance value Lminof pixels within a given width range from an arbitrary boundary by amaximum luminance value Lmax of pixels within a given width range fromthe arbitrary boundary (contrast ratio=L min/L max×100). As shown inFIGS. 5A to 5C, when the contrast ratio is 100% (FIG. 5A), no “blur”occurs, and the driver can visually check an imaged object vividly. Whenthe contrast ratio is 30% (FIG. 5B), “blur” occurs to a certain degree.However, 30% is a limit value allowing the driver to visually check theimaged object vividly. When the contrast ratio is 10% (FIG. 5C), “blur”fairly occurs, so that the driver has difficulty in visually checkingthe imaged object. That is, a condition that the contrast ratio is 30%or more is suitable to enable the driver to visually check the imagedobject.

In this embodiment, a threshold of the contrast ratio suitable forvisual checking by the driver is set to 30%. However, this threshold maybe changed depending on the size of the imaged object or the like. Forexample, in a case where a relatively small-size object is imaged by acamera, it is desirable to set the threshold to greater than 30%

Next, with reference to FIGS. 6 and 7, features of the in-vehicle imagedisplay system according to this embodiment will be described. FIG. 6 isa rear view showing the vehicle equipped with the in-vehicle imagedisplay system according to this embodiment, in association with thetraveling road zone. FIG. 7 is a top plan view of the vehicle in FIG. 6.

As shown in FIGS. 6 and 7, the left and right side cameras 7, 9 areinstalled below the left and right door mirrors 10 on the left and rightlateral portions 12 a, 12 b, respectively. In a road surface 51 in arange in which the left and right side cameras 7, 9 take images, a leftmovable zone 53 in which the vehicle 2 is movable during a time periodafter the vehicle 2 is driven forwardly under a leftward maximumsteering angle and a setup vehicle speed through until the vehicle 2 isstopped, and a right movable zone 55 in which the vehicle 2 is movableduring a time period after the vehicle 2 is driven forwardly under arightward maximum steering angle and the setup vehicle speed throughuntil the vehicle 2 is stopped, are set.

The left movable zone 53 is a zone surrounded by a front edge line 52, arear edge line 57, an outer edge line 54, and an inner edge line 59. Onthe other hand, the right movable zone 55 is a zone surrounded by afront edge line 61, a rear edge line 58, an outer edge line 56, and aninner edge line 60. Each of the left movable zone 53 and the rightmovable zone 55 is a traveling road surface section A to be watched bythe driver for safety purposes in the range in which a respective one ofthe left and right side cameras 7, 9 takes images, when pulling thevehicle 2 over. Further, a region outside the movable zone 53 (55)(traveling road surface section A) is a peripheral road surface sectionB in which a need for the driver to watch it when pulling the vehicle 2over is relatively low.

The front edge lines 52, 61 are at a reachable position in a vehicletraveling direction, which can be reached by the front edge of thevehicle 2, during a time period after the vehicle 2 is driven forwardlyat the setup vehicle speed through until the vehicle 2 is stopped(during a time period during which the vehicle 2 moves from a certainreference position (a) to a vehicle position (b)). In other words, on anassumption that the reference position (a) is defined as a position ofthe vehicle 2 as measured at a certain time when the vehicle 2 istraveling at a predetermined setup vehicle speed, the front edge lines52, 61 are at a reachable position to be reached by a contour of thefront portion 4 of the vehicle 2 located at the farthermost position inthe vehicle traveling direction, with respect to the center (O) of thevehicle 2 in the reference position (a), in a state in which the vehicle2 has been decelerated from the reference position (a) under apredetermined braking force and finally stopped. Each of the front edgelines 52, 61 extends in the vehicle-width direction in parallel with acontour line of the front portion 4 of the vehicle 2 in the referenceposition (a).

The left outer edge line 54 is at a reachable position in thevehicle-width direction, which can be reached by a corner (y1) betweenthe front portion 4 and the left lateral portion 12 a, during a timeperiod after the vehicle 2 is driven forwardly under a leftward maximumsteering angle and the setup vehicle speed through until the vehicle 2is stopped (during a time period during which the vehicle 2 moves fromthe certain reference position (a) to a vehicle position (c)). In otherwords, on the assumption that the reference position (a) is defined as aposition of the vehicle 2 as measured at a certain time when the vehicle2 is traveling at the predetermined setup vehicle speed, the leftlateral edge line 54 is at a reachable position to be reached by acontour (y1) of the left lateral portion 12 a of the vehicle 2 locatedat the farthermost position in the vehicle-width direction, with respectto the center (O) of the vehicle 2 in the reference position (a), in astate in which the vehicle 2 has been decelerated from the referenceposition (a) under a leftward maximum steering angle and a predeterminedbraking force generated by, e.g., a brake pedal depressed by the driver,and finally stopped. Each of the left outer edge line 54 extends in thevehicle traveling direction in parallel with a contour line of the leftlateral portion 12 a of the vehicle 2 in the reference position (a).

The right outer edge line 56 is at a reachable position in thevehicle-width direction, which can be reached by a corner (y2) betweenthe front portion 4 and the right lateral portion 12 b, during a timeperiod after the vehicle 2 is driven forwardly under a rightward maximumsteering angle and the setup vehicle speed through until the vehicle 2is stopped (during a time period during which the vehicle 2 moves fromthe certain reference position (a) to a vehicle position (d)). In otherwords, on the assumption that the reference position (a) is defined as aposition of the vehicle 2 as measured at a certain time when the vehicle2 is traveling at the predetermined setup vehicle speed, the rightlateral edge line 56 is at a reachable position to be reached by a part(y2) of a contour of the right lateral portion 12 b of the vehicle 2located at the farthermost position in the vehicle-width direction, withrespect to the center (O) of the vehicle 2 in the reference position(a), in a state in which the vehicle 2 has been decelerated from thereference position (a) under a rightward maximum steering angle and apredetermined braking force generated by, e.g., a brake pedal depressedby the driver, and finally stopped. Each of the right outer edge line 56extends in the vehicle traveling direction in parallel with a contourline of the right lateral portion 12 b of the vehicle 2 in the referenceposition (a).

On the assumption that a position of the vehicle 2 as measured at acertain time when the vehicle 2 is traveling at the predetermined setupvehicle speed is defined as the reference position (a), the left rearedge line 57 is at a reachable position which can be reached by thecontour of the left lateral portion 12 a of the vehicle 2, in a state inwhich the vehicle 2 has been decelerated from the reference position (a)under the leftward maximum steering angle and the predetermined brakingforce generated by, e.g., a brake pedal depressed by the driver, andfinally stopped.

Further, on the assumption that a position of the vehicle 2 as measuredat a certain time when the vehicle 2 is traveling at the predeterminedsetup vehicle speed is defined as the reference position (a), the rightrear edge line 58 is at a reachable position which can be reached by thecontour of the right lateral portion 12 b of the vehicle 2, in a statein which the vehicle 2 has been decelerated from the reference position(a) under the rightward maximum steering angle and the predeterminedbraking force generated by, e.g., a brake pedal depressed by the driver,and finally stopped.

The inner edge line 59 (60) of the movable zone 53 (55) is a line whichextends in the vehicle traveling direction along the contour line of theleft lateral portion 12 a (right lateral portion 12 b) of the vehicle 2,at a position of the lateral edge of the left lateral portion 12 a(right lateral portion 12 b) in the reference position (a). Further, aregion located inward of these inner edge lines is hidden by the vehicle2. Thus, each of the inner edge lines 59, 60 is a line representing avehicle-width directional inward limit of the road surface 51 whoseimage can be taken by a respective one of the left and right cameras 7,9.

A maximum distance L in the vehicle traveling direction of the movablezone 53(55) is a distance from the front edge of the vehicle 2 to thefront edge line 52 (61) (the reachable position in the vehicle travelingdirection). More specifically, on the assumption that the referenceposition (a) is defined as a position of the vehicle 2 as measured at acertain time when the vehicle 2 is traveling at the setup vehicle speedV, the maximum distance L is defined as a distance by which a part ofthe contour of the front portion 4 located at the farthermost positionin the vehicle traveling direction, with respect to the center (O) ofthe vehicle 2 in the reference position (a), moves in the vehicletraveling direction during a time period after the vehicle 2 isdecelerated from the reference position (a) under the predeterminedbraking force through until the vehicle 2 is stopped in the vehicleposition (b).

Further, the maximum distance L is calculated as a sum of a free runningdistance L1 which is a traveling distance of the vehicle 2 in thevehicle traveling direction as measured based on the setup vehicle speedV during a time period from a time when the driver recognizes an objectthrough until the driver starts a braking action, and a braking distanceL2 which is a traveling distance of the vehicle 2 in the vehicletraveling direction as measured based on the setup vehicle speed Vduring a time period from a time when the driver starts the brakingaction through until the vehicle 2 is stopped (L=L1+L2).

The setup vehicle speed is a prescribed fixed value, and set to a valueof 15 km/h or less, assuming pulling-over.

The free running distance L1 is a distance obtained by adding a timeperiod t1 after the driver look at the liquid crystal screen throughuntil the driver recognizes an object to a time period t2 after thedriver recognizes the object through until the driver starts a brakingaction, and multiplying the resulting sum by the setup vehicle speed(L1=(t1+t2)×V). The time periods t1, t2 are prescribed fixed values, andset, respectively, to 0.5 s and 0.75 s.

The braking distance L2 is a distance obtained by dividing the setupvehicle speed V² by a value derived by multiplying a product of afriction coefficient μ and a gravitational acceleration G by 2(L2=V²/(2×μ×G)).

A maximum distance W in the vehicle-width direction of the movable zone53 (55) is a distance from the inner edge line 59 (60) to the outer edgeline 54 (56). More specifically, on the assumption that the referenceposition (a) is defined as a position of the vehicle 2 as measured at acertain time when the vehicle 2 is traveling at the setup vehicle speedV, the maximum distance W is defined as a distance by which the cornery1 (y2) between the front portion 4 and the left lateral portion 12 a(right lateral portion 12 b) moves in the vehicle-width direction duringa time period after the vehicle 2 is decelerated from the referenceposition (a) under the leftward maximum steering angle (rightwardmaximum steering angle) and the predetermined braking force throughuntil the vehicle 2 is stopped in the vehicle position (c) or thevehicle position (d).

Further. the maximum distance W is calculated as a sum of a free runningdistance W1 which is a traveling distance of the vehicle 2 in thevehicle-width direction as measured based on the setup vehicle speed Vand the leftward maximum steering angle (rightward maximum steeringangle) during a time period from a time when the driver recognizes anobject through until the driver starts a braking action, and a brakingdistance W2 which is a traveling distance of the vehicle 2 in thevehicle-width direction as measured based on the setup vehicle speed Vand the leftward maximum steering angle (rightward maximum steeringangle) during a time period from a time when the driver starts thebraking action through until the vehicle 2 is stopped (W=W1+W2).

As shown in FIGS. 6 and 7, an optical axis 62 (64) of the wide-anglelens of the right side camera 7 (left side camera 9) is set to inclinewith respect to the vertical line by a given angle and extend toward agiven position of the traveling road surface section A so as to allowthe entire surface of the traveling road surface section A to beincluded in the central region 38 of the planer image 37. In other word,each of the optical axes 62, 64 is set to extend toward a given positionof the traveling road surface section A, such that the contrast ratio inan image region of the traveling road surface section A displayed on thedisplay unit 11 becomes 30% or more.

Further, the optical axis 62 (64) of the wide-angle lens is set toextend forwardly and obliquely outwardly so as to intersect anapproximately central region of the traveling road surface section A inthe vehicle traveling direction (forward-rearward direction) and anapproximately central region of the traveling road surface section A inthe vehicle-width direction (rightward-leftward direction). The planerimage 37 imaged through the above wide-angle lens is formed such thatthe traveling road surface section A is included in the central region38, and the peripheral road surface section B is included in theperipheral region 40.

The processing unit 15 operates to subject this planer image 37 to thesecondary processing so as not to include at least a part of an imageregion of the peripheral road surface section B, to generate a processedimage 42. More specifically, the processing unit 15 operates to displayan image region of the traveling road surface section A, while hiding,as a processed section 44, the image region of the peripheral roadsurface section B located outward of each of the outer edge lines 54,56. However, the present invention is not limited to the aboveembodiment in which only the image region of the peripheral road surfacesection B located outward of each of the outer edge lines 54, 56 ishidden as the processed section, but may be configured to hide, as theprocessed section, an image region located forward (farther), in thevehicle traveling direction, of each of the front edge lines 52, 61, oran image region located rearward, in the vehicle traveling direction, ofeach of the rear edge lines 57, 58, or may be configured to hide, as theprocessed section, the entire peripheral road surface section B.

Next, with reference to FIG. 8, an image processing method to beperformed by the processing unit 15 in this embodiment will bedescribed. FIG. 8 is a flowchart showing the image processing method. InFIG. 8, “S” denotes step.

As shown in FIG. 8, first of all, in S1, the processing unit 15 operatesto receive data about wide-angle images of the surroundings of thevehicle 2 taken by the left and right side cameras 7, 9 through thewide-angle lenses.

Subsequently, in S2, the processing unit 15 operates to correct each ofthe wide-angle images received in S1 by means of coordinate conversion,to generate a planar image.

In S3, the processing unit 15 operates to calculate, based on the setupvehicle speed V (e.g., 15 km/h) and the maximum steering angle of thevehicle, the maximum movable distance L in the vehicle travelingdirection and the maximum movable distance W in the vehicle-widthdirection. Then, the processing unit 15 operates to set the travelingroad surface section A on each of the movable zones 53, 55 in which thevehicle 2 can travel during a time period from a time when the driverrecognizes an object through until the vehicle 2 is stopped from thesetup vehicle speed V. In other words, a region outside the movable zone53 (55) (traveling road surface section A) is set as a peripheral roadsurface section B in which a need for the driver to watch it whenpulling the vehicle 2 over is relatively low.

Subsequently, in S4, the processing unit 15 operates to subject theplanar image 37 to secondary processing so as not to include at least apart of the peripheral road surface section B to generate a processedimage 42. In this way, at least a part of the peripheral road surfacesection B is hidden as the processed section 44. Specifically, an imageregion of the peripheral road surface section B located outward of theouter edge line 54 (56) is hidden as the processed section 44. However,the present invention is not limited to the above embodiment in whichonly the image region of the peripheral road surface section B locatedoutward of each of the outer edge lines 54, 56 is hidden as theprocessed section, but may be configured to hide, as the processedsection, an image region located forward (farther), in the vehicletraveling direction, of each of the front edge lines 52, 61, or an imageregion located rearward, in the vehicle traveling direction, of each ofthe rear edge lines 57, 58, or may be configured to hide, as theprocessed section, the entire peripheral road surface section B.

In S5, the processing unit 15 operates to transmit the processed image42 to the display unit 11. Then, the flow of the image processing methodis completed.

Next, (functions) advantageous effects of this embodiment will bedescribed.

The in-vehicle image display system 1 according to this embodimentcomprises: a side camera (7, 9) installed to a lateral portion (12 a, 12b) of an exterior of a vehicle 2 to face outwardly and configured totake an image of an area lateral to the vehicle 2 by using a wide-anglelens; a processing unit 15 configured to correct a wide-angle imagetaken by the side camera (7, 9) to generate a planar image 37, andprocess the planar image 37 to generate a processed image 42; and adisplay unit 11 configured to display the processed image 42 transmittedfrom the processing unit 15 on a screen. The processing unit 15 isoperable, on an assumption that: a position of the vehicle as measuredat a certain time when the vehicle is traveling at a predetermined setupvehicle speed is set as a reference position (a); and a position reachedby a corner (y1, y2) of a contour of the vehicle located at thefarthermost position with respect to the center (O) of the vehicle inthe reference position (a), in a state in which the vehicle has beendecelerated from the reference position (a) under a maximum steeringangle and a predetermined braking force and finally stopped is set as areachable position, to subject the planar image 37 to secondaryprocessing so as not to include an image region located outward, in avehicle-width direction, of the reachable position (outer edge line (54,56)).

In the in-vehicle image display system according to this embodiment, theprocessed image 42 is displayed which is subjected to the secondaryprocessing so as not to include an image region of a peripheral roadsurface section B which is other than a traveling road surface section Ato be watched by a driver for safety purposes, and in which “blur” ishighly likely to occur, wherein the peripheral road surface section B islocated outward, in the vehicle-width direction, of the reachableposition (outer edge line (54, 56)) at which the vehicle 2 havingtraveled under the maximum steering angle and the setup vehicle speed isstopped. Therefore, the driver can visually check the traveling roadsurface section A without being preoccupied with the peripheral roadsurface section B, so that it is possible to prevent distraction of thedriver's attentiveness, thereby supporting safety drive of the driver.

Preferably, in the in-vehicle image display system according to thisembodiment, the reachable position (outer edge line (54, 56)) is definedbased on: a free running distance W1 which is a traveling distance ofthe vehicle in the vehicle-width direction as measured based on thesetup vehicle speed V and the maximum steering angle during a timeperiod from a time when the driver recognizes an object through untilthe driver starts a braking action: and a braking distance W2 which is atraveling distance of the vehicle in the vehicle-width direction asmeasured based on the setup vehicle speed V and the maximum steeringangle during a time period from a time when the driver starts thebraking action through until the vehicle is stopped. According to thisfeature, the traveling road surface section A in the vehicle-widthdirection can be set accurately, so that it is possible to adequatelyperform the secondary processing so as not to include an image region ofthe peripheral road surface section B.

Preferably, in the in-vehicle image display system according to thisembodiment, an optical axis (62, 64) of the wide-angle lens is set toextend toward a give position of the traveling road surface section A,such that a contrast ratio in an image region of the traveling roadsurface section A on the movable zone (53, 55) in which the vehicle 2can travel to a reachable position (outer edge line (54, 56) becomes 30%or more. According to this feature, no “blur” occurs in the travelingroad surface section A displayed on the screen, so that the driver canvisually check the traveling road surface section A in a “blur”-freestate.

The image processing method for use in the in-vehicle image displaysystem 1 according to this embodiment comprises the steps of: receivinga wide-angle image taken by a side camera (7, 9) configured to take animage of an area lateral to a vehicle 2, through a wide-angle lens ofthe side camera; correcting the wide-angle image to generate a planarimage 37, and processing the planar image 37 to generate a processedimage 42; and on an assumption that: a position of the vehicle asmeasured at a certain time when the vehicle is traveling at apredetermined setup vehicle speed V is set as a reference position (a);and a position reached by a corner (y1, y2) of a contour of the vehiclelocated at the farthermost position with respect to the center (O) ofthe vehicle in the reference position (a), in a state in which thevehicle has been decelerated from the reference position (a) under amaximum steering angle and a predetermined braking force and finallystopped is set as a reachable position, subjecting the planar image 37to secondary processing so as not to include an image region locatedoutward, in a vehicle-width direction, of the reachable position (outeredge line (54, 56)).

In the image processing method in this embodiment, the secondaryprocessing is executed so as not to include an image region of aperipheral road surface section B which is other than a traveling roadsurface section A to be watched by a driver for safety purposes, and inwhich “blur” is highly likely to occur, wherein the peripheral roadsurface section B is located outward, in the vehicle-width direction, ofthe reachable position (outer edge line (54, 56)) at which the vehicle 2having traveled under the maximum steering angle and the setup vehiclespeed is stopped. Therefore, the driver can visually check the travelingroad surface section A without being preoccupied with the peripheralroad surface section B, so that it is possible to prevent distraction ofthe driver's attentiveness, thereby supporting safety drive of thedriver.

It should be noted that the present invention is not limited to theabove embodiment, but various changes and modifications may be madetherein without departing from the spirit and scope of the invention asset forth in appended claims. For example, as another embodiment, thetraveling road surface section A in the above embodiment may be expandedsuch that each of the rear edge line 57 of the left movable zone 53 andthe rear edge line 58 of the right movable zone 55 is set to intersect acorresponding one of the left lateral portion 12 a and the right lateralportion 12 b of the vehicle 2 in the reference position (a), in thevicinity of a middle position thereof in the vehicle travelingdirection, as shown in FIG. 9. Further, each the rear edge line 57 ofthe left movable zone 53 and the rear edge line 58 of the right movablezone 55 may be set to have a rear end extending by a length X (allowancecorresponding to the width of a human body) perpendicularly from acorresponding one of the left lateral portion 12 a and the right lateralportion 12 b of the vehicle 3. This makes it easy for the driver torecognize the presence of a person or the like being close to the leftlateral portion 12 a or the right lateral portion 12 b of the vehicle 2.Further, the above embodiment has been described based on an examplewhere the vehicle 2 is driven forwardly. Differently, when the vehicle 2is driven backwardly, the traveling road surface section A is set toextend rearwardly from the side camera (7, 9).

LIST OF REFERENCE CHARACTERS

-   -   1: in-vehicle image display system    -   2: vehicle    -   7, 9: side camera    -   11: display unit    -   15: processing unit    -   37: planer image    -   38: central region    -   40: peripheral region    -   42: processed image    -   44: processed section    -   53: left movable zone    -   55: right movable zone    -   62, 64: optical axis of wide-angle lens    -   A: traveling road surface section    -   B: peripheral road surface section

1. An in-vehicle image display system equipped in a vehicle to supportdriving of a driver, comprising: a side camera installed to a lateralportion of an exterior of the vehicle to face outwardly and configuredto take an image of an area lateral to the vehicle by using a wide-anglelens; a processing unit configured to correct a wide-angle image takenby the side camera to generate a planar image, and process the planarimage to generate a processed image; and a display unit configured todisplay the processed image transmitted from the processing unit on ascreen, wherein the processing unit is operable to set a position of thevehicle at a predetermined setup vehicle speed, as a reference position,wherein the processing unit is operable to set a position which isreached by a part of a contour of the vehicle located at a farthermostposition with respect to a center of the vehicle in the referenceposition as a reachable position, in a position of vehicle where thevehicle has stopped by being decelerated from the reference positionunder a maximum steering angle and a predetermined braking force, andwherein the processing unit is operable to execute a secondaryprocessing of the planar image so as not to include an image regionlocated outward from the reachable position in a vehicle-widthdirection, in order to generate the processed image.
 2. The in-vehicleimage display system as recited in claim 1, wherein the reachableposition is defined based on: a free running distance which is atraveling distance of the vehicle in the vehicle-width direction asmeasured based on the setup vehicle speed and the maximum steering angleduring a time period from a time when the driver recognizes an objectthrough until the driver starts a braking action; and a braking distancewhich is a traveling distance of the vehicle in the vehicle-widthdirection as measured based on the setup vehicle speed and the maximumsteering angle during a time period from a time when the driver startsthe braking action through until the vehicle is stopped.
 3. Thein-vehicle image display system as recited in claim 1, wherein anoptical axis of the wide-angle lens is set to extend toward a giveposition of a traveling road surface section, such that a contrast ratioin an image region of the traveling road surface section taken until thepart of the contour of the vehicle reaches the reachable positionbecomes 30% or more.
 4. An image processing method for an in-vehicleimage display system for supporting driving of a driver, comprising thesteps of: receiving a wide-angle image taken by a side camera configuredto take an image of an area lateral to a vehicle, through a wide-anglelens of the side camera; correcting the wide-angle image to generate aplanar image, and processing the planar image to generate a processedimage; setting a position of the vehicle at a predetermined setupvehicle speed, as a reference position; setting a position which isreached by a part of a contour of the vehicle located at a farthermostposition with respect to a center of the vehicle in the referenceposition as a reachable position, in a position of vehicle where thevehicle has stopped by being decelerated from the reference positionunder a maximum steering angle and a predetermined braking force; andexecuting a secondary processing of the planar image so as not toinclude an image region located outward from the reachable position in avehicle-width direction, in order to generate the processed image.